The present, invention relates in general to dynamoelectric machines, such as electric motors and generators, and in particular to an improved method for controlling the flow of lubricant within the motor.
One type of electric motor, for example, the 51 frame fan motor manufactured by the General Electric Co., employs a self-contained lubricating system for lubricating the rotor shaft sleeve bearing and for carrying heat out of the bearing. U.S. Pat. No. 2,522,985 to Harl C. Bradley is an example of this type of motor.
The motor includes a reservoir located coaxially with the rotor shaft comprising a lubricant saturated absorbent material, such as wool felt, and a wool felt wick which transfers the lubricant, such as an appropriate oil, to a spiral groove on the rotor shaft. As the shaft rotates, lubricant is drawn from the reservoir and pumped along the shaft to establish a lubricant film between the shaft and sleeve bearing which rotatably supports it. Since the lubricant flows out of the end of the bearing, motors of this type are conventionally provided with a lubricant thrower or slinger in the form of an enlarged diameter ring on the shaft which throws any lubricant which reaches the slinger radially outward into an enclosing oil well cover. In some cases, an annular splash wick is positioned within the oil cover so that lubricant thrown radially outward will be absorbed by it and be conveyed more readily back to the reservoir through passages in the rotor supporting structure.
Although the previously used lubricant slinger has been effective in assisting in returning the lubricant back to the reservoir, some motors of this type have been subject to sporadic lubricant leakage problems. The oil circulation path between the reservoir and end of the bearing can be effectively sealed in the rearward portion of the motor, but the inner oil well cover is open on its forward end to permit passage of the rotor shaft therethrough. Since lubricant is thrown radially outwardly against the oil well cover, on some occasions, the lubricant tends to migrate forwardly beyond the slinger and out the forward end of the oil cover where it is lost into the stator compartment. This not only results in a decrease in the lubricant available for circulation through the bearing, but the lubricant can begin to leak from the motor case.
It has been found that prior lubricant slingers, such as the enlarged rotor shaft slingers as shown in U.S. Pat. No. 2,522,985 or the cylindrical oil slingers comprising a cylindrical washer-like element affixed to the rotor shaft, tend to throw the lubricant off in a fanned out pattern. Although most of the lubricant is slung radially outward, a portion of the lubricant slung by the forward and rear edges of the prior slingers is thrown off at angles to the shaft axis such that the lubricant has forward and rearward, respectively, components of velocity. Thus, the lubricant thrown off the forward edge of the slinger has a significant component of velocity towards the open end of the inner oil well cover, thereby contributing to the aforementioned migration of lubricant out into the stator housing of the motor.
Motors of the type shown in U.S. Pat. No. 2,522,985 are designed to be operated with the shaft horizontal, with the shaft vertical and the reservoir at the bottom, or any position inbetween. If the motor becomes tilted such that the forward end of the shaft at the opening in the inner oil well cover is lower than the end of the shaft in the reservoir, however, lubricant tends to pool at the open end of the inner oil well cover. This not only prevents the lubricant from being recirculated, but can increase the possibility of its being discharged through the forward opening in the inner oil well cover and thrown outwardly by the rotor.
The problem of oil leakage described above is not necessarily limited to the type of motor described in U.S. Pat. No. 2,522,985. Other dynamoelectric machines, such as motors and generators, may exhibit similar problems where the oil being pumped between bearing surfaces tends to migrate out of a semisealed oil circulation system.